Fig. 4

Whole mount in situ hybridization for Ml-Vasa1 following the improved fixation protocol (a, b antisense riboprobe, c, d sense control probe). Vasa has been shown to label germ line precursors in the gonads of another species of ctenophore [8]. a, c. Large (2–3 mm) cydippid stage animals viewed by compound dissecting microscope. Oral side faces up. b, d. Compound microscope views of comb rows and underlying gonad tissue. Sense control probe shows no staining in the gonad. All scale bars = 100 μm